Following the use of most modern separation techniques, further treatment of the separated components of a sample is required to obtain more complete information about the nature of the components. For example, methods of functional genomics (e.g., differential display (Liang et al., Science 257:967-971, 1992), AFLP (Vos et al., Nucl. Acid Res. 23:4407-4414, 1995), etc.) produce a pattern of separated DNA fragments, but the products of differentially expressed genes have to be identified separately. As another example, methods to discriminate mutations such as constant denaturant capillary electrophoresis (CDCE) also require subsequent determination of the specific mutation (Khrapko et al., Nucl. Acid Res. 22:364-369, 1994). To perform such a multidimensional analysis, a high throughput preparative separation system capable of collecting comprehensively all components of the sample mixture would be desirable.
Current micropreparative techniques for purification and fraction collection generally use either chromatography or electrophoresis for separation of the sample components. Fully automated single column systems are available, allowing fractionation and collection of specific sample components per run (Karger et al., U.S. Pat. No. 5,571,398 (1996); Carson et al., U.S. Pat. No. 5,126,025 (1992)). When fractions from multiple lanes are required, e.g., of DNA fragments, slab gel electrophoresis can be used for the simultaneous separation of the samples, followed by manual recovery of the desired fractions from the gel. This process is slow, labor intensive and imprecise. In another analytical approach, DNA fragments can be collected onto a membrane using direct transfer electrophoresis (Richterich et al., Meth. Enzymol. 218:187-222 1993). However, recovery of the samples from the membrane is slow and difficult.